The present invention relates to a method of inspecting surfaces of materials to be examined wherein the surface is scanned line by line by means of an optical measurement pickup and the signal furnished by the measurement pickup is processed to provide information about the surface consistency of the material being examined.
The invention further relates to a surface inspection system including an optical measurement pickup, particularly a laser scanner or a video camera, which line by line scans the surface structure of a material to be examined, and a signal evaluation unit which processes the signal furnished by the measurement pickup.
Such methods and systems are used, for example, to detect surface flaws during the production or processing of metal, paper and textile panels. In these systems, for example, the material transported on a conveyor belt is moved past a measurement pickup which scans the surface of this material line by line, with this measurement pickup furnishing a signal that is representative of the material surface and is subsequently evaluated by a flaw detection unit.
In these systems, it is considered to be a drawback that they either operate with an insufficiently high resolution, so that the reliability of the systems is limited and thus reliable flaw detection cannot be ensured, or the resolution is high enough to ensure reliable flaw detection but this can be realized only at high manufacturing expense, and thus considerably reduce the economical utility of the system.
It may further be a problem to detect faulty patterns in the material surface that extend over a certain area since for this purpose, on the one hand, a number of scanned lines that cover the faulty pattern must be stored and, on the other hand, it must also be ensured that a subsequent association of the individual scanned lines with their position on the material surface to be examined must be possible. This poses problems, particularly if the material to be examined does not move past the measurement pickup at a constant speed.